Hi Lianachan,
It's definitely not an Class III stone, it's a lot more primitive than that. it's just a huge cross gouged out of what is almost certainly an old standing stone
as for this particular <a href="http://www.themodernantiquarian.com/site/5085">Kilmorich</a>, Watson believes it contains the name Muireadhach which may be St Muireadhach, abbot of Hi, who died in 1011 (cf St Muireach's Well at Mains of Kilmorick in the 1845 Statistical Account, p997)
the field at Kilmorich is very interesting actually (<a href+"http://www.themodernantiquarian.com/site/5085">click here for it's page on TMA</a>, with what's probably a long barrow sticking out of a round cairn
the Scottish Megaraks visited it back in 2002, <a href="http://www.andysweet.co.uk/stones/megaraks/october2002-2.html">here</a>
Cheers
Andy